Paronychia Underlying Cause
A paronychia is caused by an infection with bacteria that are normally on the surface of the skin.
Steps that lead to the infection include:
- The nail causes a small injury to the skin
- The bacteria enter the tissue beneath the skin surface
- The bacteria start to grow, causing an infection, swelling and pain
- Daniel CR 3rd, Daniel MP, Daniel CM, Sullivan S, Ellis G. Chronic paronychia and onycholysis: a thirteen-year experience. Cutis. 1996 Dec;58(6):397-401. 
- Rockwell PG. Acute and chronic paronychia. Am Fam Physician. 2001 Mar 15;63(6):1113-6. 
- Tosti A, Piraccini BM, Ghetti E, Colombo MD. Topical steroids versus systemic antifungals in the treatment of chronic paronychia: an open, randomized double-blind and double dummy study. J Am Acad Dermatol. 2002 Jul;47(1):73-6.